Serial printing device

ABSTRACT

A serial printing device is provided with a rotatable disc having a set of flexible tongues each one engageable by a hammer to strike against the paper. The disc is rotated by a stepping motor controlled by electronic circuits to bring the selected type on the printing point through the shortest path. The disc is also mounted on a carriage which is moved by another stepping motor controlled by an electronic circuit. The carriage and the relevant guides are mounted on a frame pivotable on a vertical shaft mounting one of the ribbon spools, in order to remove the disc from the carriage and to facilitate the insertion of fresh paper.

United States Patent Ponzano [54] SERIAL PRINTING DEVICE [72] Inventor: Gian LuigiPonzano,lvrea,ltaly [73] Assignee: Ing. C. Olivetti & C., S.p.A., Ivrea (Torino), Italy [22] Filed: May 18,1970

[21] Appl.No.: 38,208

[30] Foreign Application Priority Data May 23, 1969 ltaly ..51959 A/69 [52] US. Cl. ..l97/53, 101/93 C, 197/18, 197/133A [51] Int. Cl. ..B41j 1/22 [58] Field of Search ..l97/6.6, 133 A, 53, 48, 18; 101/93 [56] References Cited UNITED STATES PATENTS 3,283,871 11/1966 Becking et al ..l97/20 3,291,292 12/1966 3,366,214 1/1968 3,282,389 11/1966 2,236,663 4/1941 [151 3,707,214 [451 Dec. 26,1972

3,185,075 5/1965 McGregor et a1 ..10l/93 C 2,427,611 9/1947 Lane ..197/133 A X 1,564,408 12/1925 Crcws....

1,362,544 12/1920 Smith ..l9 7/l33 A 2,927,676 3/1960 Abbondanza l 97/6.6 3,356,199 12/1967 Robinson ..197/53 X Primary Examiner-Edgar S. Burr Attorney-Birch, Swindler, McKie and Beckett [57 ABSTRACT A serial printing device is provided with a rotatable disc having a set of flexible tongues each one engageable bya hammer to strike against the paper. The disc is rotated by a stepping motor controlled by electronic circuits to bring the selected type on the printing point through the shortest path. The disc is also mounted on a carriage which is moved by another stepping motor controlled by an electronic circuit.

The carriage and the relevant guides are mounted on a frame pivotable on a vertical shaft mounting one of the ribbon spools, in order to remove the disc from the carriage and to facilitate the insertion of fresh paper.

14 Claims, 6 Drawing Figures PATENTED 25 1973 3,707,214

sum 1 OF 4 ENTOR.

INV GIAN LUIGI PONZANO PATENTEDBEBZE m2 3.707.214

SHEEI 2 OF 4 v INVENTOR. GIAN LUGI PONZANO BY M} XMQJ WAG/{Q4 96M ATTORNEY SERIAL PRINTING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printing arrangement for teleprinters and data processing systems in general, comprising a support for the paper, a type unit and a carriage which moves either the support or the type unit.

2. Description of the Prior Art It is known to shift the carriage in the two directions by a reversible electric motor permanently connected to the carriage through the medium of a closed flexible element.

1 Various printing arrangements are known in which the carriage is generally shifted step by step in one direction under the control of an escapement device and is shifted for the continuous tabulation or return travels until it is stopped against the corresponding stops. v In other known printing arrangements, the carriage is shifted by a motor during the printing and in the tabulation travels and is brought back to the beginning by the action of a spring, the continuous travels of the carriage being also controlled in this case by mechanical stops.

There are also known other printing arrangements in which the carriage is shifted by a motor in both directions, for example through the medium of a pair of dog clutches. These arrangements, however, are very slow, bulky and costly.

In another known arrangement, the carriage is shifted in the two directions by a reversible electric motor through the medium of a pair of electromagnetic clutches, one for advance and the other for return.The step-by-step shifting of the carriage is controlled by a series of contacts carried by a disc which is rotated by the shifting of the carriage. This arrangement has the same disadvantages of slowness and bulkiness referred to hereinbefore and is moreover unreliable in operation.

There are also known single-element printing devices in which the selection of the character is effected by the shortest route through a reversible stepping motor. Finally, other known printing devices use as the printing element a disc having tongues and which is positioned through movement-summing selection devices or is rotated continuously to effect the printing on the fly.

SUMMARY OF THE INVENTION The object of the present invention is to combine a number of elements known from the above-described arrangements with other elements that are new to create an improved printing arrangement which is of limited over-all dimensions, fast and reliable in operation and of relatively low cost. The invention enables the shifting of the carriage to be controlled by means of a single reversible electric motor without the use of mechanical stops or electric contacts for controlling the travels of the carriage.

According to the invention there is provided a serial printing arrangement comprising a support for the paper, a type unit and a carriage for producing the relative transverse change of position between the support and the type unit, the carriage being shifted in the two directions by a reversible electric motor permanently BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view from the right of a continuous-form printer incorporating the printing arrangement according to the invention;

FIG. 2 is a front perspective view from the right of a detail of FIG. 1 on a larger scale; I

FIG. 3 is a partial plan view of the printer of FIG. 1;

FIGS. 4 and 5 show a block diagram of the electronic controller of the printer of FIG. 1;

FIG. 6 is a diagram showing the combination FIGS. 4 and 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS General description Referring to FIG. 1, the printer includes a "fixed frame 11 having two side walls 12 and 13 on the left and right, respectively, supporting a platen 14 so that it can rotate therein. A grooved shaft 16 is rotatable in the side walls 12 and 13 of the frame 11, the shaftbeing rotated synchronously with the platen 14 by means of two pulleys 17 and 18 and a toothed belt 19. On'the shaft 16 there are fixed two drums 21 and 22 equipped with draw pins 23 adapted to secure thecarrying along of the usual continuous forms 24 having perforated margins. The forms are held in position by means of paper guide plates 26. The transverse position of the drums 21 and 22 along the shaft 16 is adjustable, for example by means of screws 27, so asto suit this position to the width of the forms.

To the top edges of the side walls 12 and 13 of the frame 11 there is fixed, for example by means of two screws 28, a bar 29 disposed parallel to the platen l4 and having a transverse slot 31 along which a slide 32 can be moved by means of an operating lug 33. The slide 32 is equipped with a knife or blade, not visible in the drawing, which extends through the slot 31 and is adapted to cut the continuous forms 24 transversely.

The platen 14 may also support single sheets which are introduced from the rear of the platen 14 and are guided in known manner by a lower paper guide plate 34 and a series of rollers 36. A pair of upper papergripping rollers 37 carried by a bar 38 ensure that both the continuous forms 24 and the single sheets are kept in contact with the platen 14. The vertical line-spacing and tabulating movements are effected, through the medium of two pulleys 39 and 41 and a toothed belt 42, by an electric motor 43 under the control of an endless loop of punched tape in a manner known per se, or by means of the knob 46.

To the left side 12 of the frame 11 there are fixed two drilled horizontal projections 47 and 48 supporting a vertical shaft 49 rotatable therein. Two drilled horizontal projections 51 and 52 fixed to a side wall 53 of a frame 54 can turn about the shaft 49. The side wall 53 is co-planar in the closed position with the side 12 of the fixed frame 11. Similarly, a second side wall 56 of the movable frame 54 isco-planer inthe closed position with the respective right side 13 of the frame 11. A hooked lever 57 pivoted at 58 on the side wall 13 normally engages in a projection (not shown in the drawing) of the movable frame 54 to lock the frame 54 to the frame 11. By operating the lever 57, the right-hand side of the frame 54 can be released and the frame can then be swung anticlockwise about the shaft 49 and brought into the position shown in dash lines in FIG. 3. This allows access to the printing face of the disc 69 for normal servicing or replacement of the disc itself. Moreover, with the frame 54 in the open position, insertion of the continuous forms can be effected easily.

To the side walls 53 and 56 of the movable frame 54 there are fixed two bars 59 and'61 of circular cross-section which are parallel to the platen 14 in the closed position. Two bushes 62' and 63 of a carriage 64 can slide on the bars 59 and'6l. Fixed to the carriage 64 (FIG. 2) IS A reversible stepping motor 66 the driving shaft 67 of which is disposed horizontally and is perpendicular to the bars 59 and 61. On the shaft'67 there is keyed a hub 68 on which a type disc 69 can be mounted removably, but in an angularly defined manner. The type disc is therefore disposed in a plane parallel to the platen 14. The disc 69 is made of elastically flexible material, for example spring steel, and has its annular peripheral portion subdivided by 48 radial slits which define an equal number of sector-shaped tongues 71 on each of which a printing type 73 is stamped. The type or character 73 selected for printing is substantially at the same height as the axis of the platen 14.

On a bracket 74 of the carriage 64 there is fixed a pin 76 on which there is pivoted a hammer 77 normally bearing against a stop stud 78 through the action of a spring 79. The hammer 77 carries the movable annature 81 of an electromagnet 82, the electromagnet being also fixed to the bracket 74. Energization of the electromagnet 82 causes the attraction of the armature 81 and, consequently, the striking of the hammer 77 perpendicularly to the disc 69 against that tongue 71 behind the hammer which is selected for printing. Due to the effect of the blow, the tongue 71 bends with respect to the disc 69 and strikes, through an inked ribbon 83, the paper arranged on the platen 14, imprinting the selected character on the paper.

The carriage 64 has a projection 80 to which an illuminating device 85 and a photoelectric cell 90 are fixed. The light transmitting elements of the device 85 and the cell 90 are constituted, for example, by a pair of optical fibers 95 disposed at 180 with respect to the hammer 77 in front of the opposite face to the: printing face of the disc 69. On the first-mentioned face, each tongue 71 is covered with an opaque black coating, with the exception of a single tongue 72 which is disposed in front of the optical fibers 95 in the drawing and which, on the contrary, is reflecting. in consequence, the light emitted by the device 85 is received by the cell 90 only in correspondence with the passage of the reflecting tongue 72 in front of the pair of optical fibers 95. A flexible wire 84 (FIG. 1) is fixed byits two ends to a projection 86 of the carriage 64. The wire 84 passes through a pair of holes 87 in the side walls 53 and 56 of the movable frame 54 and is wound on the left around a return pulley 88 (FIG. 3) rotatable on a support 89 fast with the side wall 53 of the frame 54. On the right, the wire 84 is wound round a driving puiley 91 keyed on a shaft 92 of another reversible stepping motor 93 fixed to asupport 94 integral with the side wall 56 of the movable frame 54.

On another projection (FIG. 2) of the carriage 64 there are fixed a second illuminating device 96 and a secondphotoelectric cell 97, the optical transmitting fibers 98 of which appear at the front of the frame 54. On a horizontal surface of the frame 54 there is fixed a reflecting plate 99 which causes the beam emitted by the device 96 to reach the cell 97 when the carriage 64 is in the extreme left-hand position. v

The inked ribbon 83 (FIG. 1) is'guided transversely of the printer between two pins 101' fixed to the two side walls 53 and 56 of the frame 54. The ribbon 83 is shifted from one to the other of two spools 102 and 103 which are respectively fixed on the shaft 49 and a second shaft 104 rotatable in two projections or extensions 106 and 107 integral with the side wall 56. The shafts 49 and 104 are rotated selectively in known manner, for example by deriving their motion from that of the pulleys 88 and 91. The two spools 102 and 103 are arranged at slightly different heights so that the ribbon is disposed in front of the platen in an inclined position and can be used over the whole of its height. The ribbon is moreover guided in the vicinity of the printing point by two pairs of pins 108 and 109 (FIG. 2) fixed to the bracket 74 of the carriage64.

SELECTION OF THE CHARACTER TO BE PRINTED The stepping motor 66 includes a stator having three windings 111, 112, 113 (FIG. 4) fed sequentially by a series of pulses supplied by three amplifiers 114, 116, 1 17 connected by the lines 118, 119, 121 to the outputs of a counter 122. The number of pairs of poles of which the rotor of the motor 66 is formed is such that for each pulse energizing the stator windings the driving shaft 67 rotates through an angular step equal to the angular step or pitch of the types or characters 73 on the disc 69, in a manner known per se.

The counter 122 has a capacity of three and is adapted to count forward the pulses entering at a first input thereof along a line 123 and to count backward the pulses entering at a second input thereof along a line 124. The pulses entering the first input of the counter 122 activate the output lines in the order 118, 119, 121, 118 and so on, and energize the stator windings in the sequence 111, 112, 113, 111 and so on,

causing a rotation of the rotor clockwise in FIG. 1 for an equal number of steps. The pulses entering the second input of the counter 122 (FIG. 4) activate the output lines in the order 118, 121, 119, 118 and so on, and energize the stator windings in the sequence 111, 1 13, 1 12, 1 1 1 and so on, causing a rotation of the rotor anticlockwise in MG. 1 for an equal number of steps.

The motor 66 stops from time to time together with the disc 69 in the position corresponding to the last character printed. From this position, by choosing the order of energization of the windings suitably, the new character to be printed can be brought to the printing point along the shorter arc, that is within 180 of rota tion of the disc 69. Moreover, by'transmitting to the stator windings a number of pulses not greater than one half of the characters 73 and equal to the steps for which the disc 69 must rotate, any character 73 on the disc 69 can be selected for printing.

The pulses to be sent to the counter 122 are generated by a generator 126 which can be activated at its input by a signal R through an OR gate 127 and an AND gate 128. This generator then generates in known manner a series of selecting pulses ll at the frequency corresponding to the speed of rotation of the disc 69 for the selection of the characters, for example a frequency of 600 c.p.s.

The selecting pulses 11 are sent through an AND gate 129 to twoAND gates 130 and 131 and from here to the two inputs of the counter 122. According to which of the two AND gates 130 and 131 is preset and, therefore, according to which input is concerned, the pulses Il produce rotary movements of the disc 69 clockwise or anticlockwise.

The pulses l1 entering the counter 122 are also sent to a selection counter 132 which has a capacity equal to the number of characters 73 on the disc 69 and is adapted to count forward the pulses l1 coming from the gate 130 and to count backward the pulses I1 coming from the gate 131.

On the passage of the reflecting tongue 72 (FIG. 2) in front of the optical fibers, the photoelectric cell 90 generates a signal which enters a third input of the counter 132 (FIG. 4) and resets it to zero.

The counter 132 is normally loaded with a number corresponding to the character 73 on the disc moving by in front of the hammer 77. This number evolves following step by step the clockwise or anticlockwise rotary movements of the disc 69. 7

By sending a predetermined number of pulses to the first input of the counter 122, the disc 69 rotates clockwise for an equal number of steps, arranging the corresponding character in the printing position, and at the same time the selection counter 132 accumulates an equal number of pulses. Similarly, if a number of pulses enters the second input of the counter 122, the disc 69 rotates anticlockwise for the same number of steps and the counter 132 subtracts an equal number of pulses, as a result of which the counter 132 constantly indicates which character is in the printing position. The number recorded in the counter 132 is sent through a series of lines 133 to a comparison circuit 134 known per se where it is compared with a selection number read from a store 190 given by a keyboard and representing the character to be selected for printing. This number is sent to the circuit 134 through a series of lines 135. The circuit 134 is adapted to generate a signal C when equality is obtained between the position number and the selection number. I

Another pulse generator 136 can be activated at its input by a signal which passes through an OR gate 137 and an AND gate 138, generating at an output a series of analysis pulses 12 at a frequency substantially higher with respect to that of the selecting pulses 11, for example a frequency of 500 kc.p.s.

The analysis pulses 12 are sent to a fourth input of the selection counter 132 and to a first input of another counter 139 having a capacity equal to the number of I half of the counter 139, the'counter generates a signal f3 When the counter 139 is full it moreover generates a signal 14.

The operation of the circuit described forthe choice of the'sense of rotation of the disc 69, selection of the character 73 and printing is as follows.

After the printing of a character, the counter 139 still emits the full signal I4, while the circuit 134 emits the signal C. On reception of the numbercorresponding to the character to be printed on the lines 135, the circuit '134 compares this number with the number on the disc 69. If the two numbers do-not coincide, a series of analysis pulses I2 is .sent to the counter 132 until coincidence is obtained. To this end, the signal C indicating non-coincidence reaches the AND gate 138 through the CR gate 137 .The same signal C is moreover sent to the AND gate 128 through a delay circuit 141. In coincidence with a signal l? indicating that the generator 126 is not activated, the gate 138 then immediately activates the high-frequency generator 136, which sends a train of pulses I2 to the two counters 132 and 139. The latter counter then begins to count starting from the full condition, as a result of which the first pulse 12 eliminates the signal l4 before the delay cir cuit'141 has activated the gate 128, so that the generator 126 is not then affected. At the same time, the contents of the counter 132 are compared by the circuit 134 through the lines 133 with the number arriving from the lines 135. When the circuit 134 detects coincidence of the two numbers it emits a signal C. if, at that instant, the counter l39is in the first half of its capacity, it presets a AND gate 142 through the signal [3. The signal C then switches a flip-flop 143 to a first state presetting the gate 131), as a result of which the counter 122 is preset to command the clockwise rotation of the motor 66. If, on the other hand, at said instant, the counter 139 is in the second half of its capacity, the signal 13 presets a AND gate 144. The signal C then switches the flip-flop 143 to a second state, presetting the gate 131, as a result of which the counter 122 is preset to command the anticlockwise rotation of the motor 66. The generator 136, however, continues to generate the signals 12 until the counter 139 reaches the full condition. At this instant, the counter 139 emits the signal 14, which causes the gate 128 to emit the signal R. The signal R then ceases and by means of the gate 138 causes the generator 136 to be blocked. The signal R then presets the generator 126 for activation. Finally, the signal I4 is also applied to an AND gate 145. Since the counter 132 has the same capacity as the counter 139, when the signal 14 is generated the counter 132 is again exactly in the state which it had at the beginning of the operation.

It is to be noted, however, that the complete cycle of 7 The generator 126 now Fills a train of low-frequency pulses which, through the AND gate 129 which is preset by the signal I2, activates thatone of the two gates 130, 131 which has been preset by the flip-flop 143. The pulses emitted by the generator 126 are therefore sent to the counter 122, which energizes the windings 111, 112 and 113 in the order corresponding to' the sense of rotation desired for the motor 66. The gate 130 or 131 sends the same number of pulses to the counter 132 to be added or subtracted, respectively, as aresult of which this counter approaches step by step the state that is laid down by the signals on the lines 135.

When the circuit 134 now detects coincidence of the signals on the lines 133 with those on the lines 135, it againemits a signal C which inhibits the generator 126 through the circuit 141 and the gates 128 and 127. The motor 66 therefore stops together with the disc 69 (FIG. 2) with the character 73 in front of the hammer 77.

Moreover, the signal. C in coincidence with the signal I4"(FIG. 4) and a signal M which is generated in the manner whichwill be described hereinafter, passes through the" AND gate 145 and reaches an amplifier 146 which generatesa power signal. This then energizes the electromagnet 82 controlling the armature 81 (FIG. 2) of the hammer 77, which then effects the printing of the character 73 selected.

When the amplifier 146 (FIG. 4) energizes the electromagnet 82, it generates a signal S which produces the calling-up of the following character from the store or from the keyboard in a manner known per se.

If the character called up is identical to that previously printed, the signal C, acting through the gate 145 and the amplifier 146, immediately causes a second printing of the same character to take place.

On the starting of the printer, it is advisable to synchronize the disc 69 with the counter 132. To this end, a pulse Z is generated by means of a manually or automatically operated contact 147 (FIG. 5) and over a line 148 this pulse enters a first input of the flip-flop 140 (FIG. 4). The flip-flop then emits a signal which resets the analysis counter 139 and activates the generator 126 through the OR gate 127. The generator 126 begins to supply the selecting pulses 11. The signal R then blocks the gate 138 and therefore prevents the generator 136 generating the pulses 12. Through the gate 129, already preset owing to the presence of I2,

and through the gate 130 or 131, the selecting pulses I1 reach the counter 122 and command the rotation of the disc 69 in the sense determined by the state of the flipflop 143. The rotation of the disc 69 (FIG. 2) continues until such time as the reflecting tongue 72 is disposed in 8 CARRIAGE'SHIFT The stepping motor 93 (FIG. 1) includes a stator with four windings 149, 150, 151, 152 (FIG. 5) fed sequentially by the pulses supplied byfour amplifiers 153, 154, 155, 156 connected to four AND gates 157, 158, 159, 160. Each of these gates is connected to two out of four outputs 161, 162, 163,164 of a counter 165. Each output is therefore connected to two of the rear gates 157, 158, 159, 160 in the mannershown in FIG. 5. The number of pairs of poles of which the rotor of the motor 93 is formed and the diameter of the driving pulley 91 (FIG. 1) are such that for each pulse energizing the stator windings the carriage 64 is shifted by one step.

The counter has two stages and is adapted to count forward :the pulses comingfrom an AND gate 166 and to count backward the pulses coming from an AND gate 167. For each state of the counter 165, two of its outputs are activated and two are deactivated, the signals at the outputs 163 and l64 being the negations of thesignals at the outputs 161 and 162. The pulses coming from the gate 166 activate sequentially the pairs of outputs 161, 164; 162, 163; 163, 164; 161,

162. The corresponding pairs of AND gates transmit the signals in the vorder 157, 158, 159, 160, 157 and so on and, through the corresponding amplifiers 153, 154, 155, 156, 153 and so on, cause the motor 93 to rotate clockwise in FIG. 1 step by step, consequently shifting the carriage 64 to the right. The pulses entering the counter 165 and coming from the gate 167 activate the pairs of outputs in the order 161, 164; 161, 162; 163, 164; 162, 163. The corresponding AND gates are activated in the order 157, 160, 159, 158 and so on and, through the amplifiers 153, 156, 155, 154, 153 andso on, cause the motor 93 to rotate anticlockwise in FIG.

, 1, consequently shifting the carriage 64 to the left;

The printer includes a pulse generator 168 (FIG. 5) adapted to generate a series of pulses at a frequency corresponding to the spacing speed of the carriage 64. These pulses are sent through an AND gate 169 and an OR gate 170 to the AND gates 166 and 167. According to which of the two AND gates 166 and 167 is preset, the pulses command shifts of the carriage 64 to the right or to the left. I

The pulses leaving the AND gate 166 are sent to a first input of a carriage position counter 171, while the pulses leaving the AND gate 167 are sent to a second input of the counter 171. This has a capacity equal to the number of positions for which the carriage 64 can shift along a printing line and is adapted to count forward the pulses coming from the gate 166 and to count backward the pulses coming from the gate 167. The counter 171 is adapted to generate a signal I5 when it is at zero and a signal I6 when it is in the full state.

The counter 171, by counting forward or backward the pulses commanding the clockwise or anticlockwise rotation of the motor 93, is adapted to record the direction of movement and the number of spaces for which the carriage 64 (FIG. 1) is shifted with respect to a zero position, which is assigned to the extreme lefthand position of the carriage 64. When the carriage 64 occupies the zero position, the optical fibers 98 are in front of the reflecting plate 99, as a result of which the photoelectric cell 97 generates a signal which is sent to a third input of the counter 171 (FIG. 5) and resets it to zero. In this way direct correspondence is established between each position occupied by the carriage 64 along the printing line and the number recorded in the counter 171.

The number recorded in the counter 171 is sent through a series of lines 172 to a first input of a comparison circuit 173, where it is compared with a number indicating the position that the character to be printed is to occupy in theline and stored in the store in association with the number indicating the character itself. The number indicating the position is read and sent through a series of lines 174 to a second input of the comparison circuit 173. If the number coming from the lines 174 is greater than that coming from the lines 172, the carriage 64 is to the left of theprinting point, while if the number coming from the lines 172 is greater the carriage 64 is to the right of the printing point. In the first case, the circuit 173 sends a spacing command signal M1 to an OR gate 175'and to an OR gate 176, while in the second case it sends a signal M2 to an OR gate 177. The comparison circuit 173 can be rendered inactive by a blocking circuit 178 controlled by an CR gate 179. To the gate 179 there is applied a signal N generated in known manner and indicating absence of the position number on the lines 174. Therefore, in the absence of data in the store 190 or in the event of command of the printer from the keyboard, the comparisoncircuit 173 remains inactive.

The OR gate 177 is connected to the OR gate 176, which is connected in turn to the AND gate 169. The signals issuing from the gate 176 also arrive at an OR gate 180 from which is derived the consent signal M, the negation M of which controls the printing of the character selected, as already seen hereinbefore. In this case, therefore, the signal M indicates that the carriage is in the shifting stage. The signals issuing from the OR gate 175 arrive at the AND gate 166, at which the signal 16 also arrives. The transmission of the command for shifting to the right is thus prevented when the carriage 64 is in the extreme right-hand position. The signals issuing from the OR gap 181 arrive at the AND gate 167, at which the signal also arrives through an OR gate 182. The transmission of the command for shifting to the left is thus prevented when the carriage is in the extreme left-hand position.

Let it be supposed first of all that the number coming from the lines 174 is greater than that coming from the lines 172. Through the gate 176, the comparison circuit 173 then presets the gate 169 and, through the gate 1 75, presets the gate 166 then conditioned by the signal 16. The pulses supplied by the generator 168 reach the counter 165 through the gates 169 and .166, causing the motor 93 to rotate clockwise and the carriage 64 to shift to the right. These movements are counted by the counter 171, in which the number recorded will evolve in an increasing sense. When equality is reached between the number coming from the lines 174 and that coming from the lines 172, the signal M1 is cancelled. Since the presetting at the AND gate 167 is now lacking, the pulses supplied by the generator, 168 cannot reach the counter 165, as a result of which the shifting of the carriage 64 ceases. The cancellation of the signal M1 also cancels the signal M emitted by the gate 180, so that the signal M for presetting the gate 167 (FIG. 4) commands the printing of the character selected in the manner hereinbefore described.

Similarly, if the number coming from the lines 172 (FIG. 5) is greater than that coming from the lines 174, the comparison circuit 173 presets the gate 169 through the gates 177 and 176 and presets the gate 167 through the gates 177 and 181, which gate 167 then conditioned through the gate l82by the signal IS. The pulses supplied by the generator 168 now arrive at the counter through the gates 169 and 167 and cause the carriage 64 to shift to the left. The steps of the carriage 64 are counted backward by the counter 171. On equality of the two numbers being reached, the movements of the carriage 64 cease and, as in the preceding case, consent for the printing of the character selected is transmitted.

0n the starting of the printer, it is advisable to synchronize the carriage 64 with the counter 171. To this end, the pulse Z is generated by means of the contact 147 and enters a first input of a flip-flop 184 through an OR gate 183. The flip-flop then emits a signal M3 which is sent to the OR gates 179, 177, 182. The signal issuing from the gate 179 commands the blocking circuit 178 and renders the comparison circuit 173 inactive. The signal issuing from the gate 177 presets the gate 169 through the gate 176, while said signal issuing from the gate 177 arrives by means of the OR gate 181 at the AND gate 167. The pulses supplied by the generator 168 can therefore reach the counter 165, which commands the shifting of the carriage 64 to the left, that is towards the zero position. These movements also take place when the counter 171 is reset to zero, since the signal M3 at the gate 182 replaces the effect of the signal 15, which disappears precisely when the counter 171 is reset.

When the extreme left-hand position is reached, the photoelectric cell 97 generates a signal which is sent to a second input of the flip-flop 164 and cancels the signal M3. The carriage 64 is now in the extreme lefthand'position, while the counter 171 is reset to zero and the comparison circuit 173 is ready to carry out the commands for shifting of the carriage 64 to the right. During the normal operation ofthe printer, every time the carriage reaches the zero position the photoelectric cell 97 resets the counter 171, ensuring constant synchronization between the position of the carriage and the counter.

MANUAL OPERATION OF THE PRINTER 1n the case where the printer is operated from a keyboard, the shifting of the carriage 64 takes place after the printing of the character selected, or on the depression of an operative key. In each case, the signal N, indicating the absence of information from the store, activates the blocking circuit 178 by means of the OR gate 179 and renders the comparison circuit 173 inactive.

in the case of the printing of a character set on the keyboard, simultaneously with the number representing the character to be selected there is generated a signal M4 for advance by one step, which presets the gates 166 and 167 through a second input of the OR gate and presets an AND gate 185, the output of which is connected to the gate 175. The printing of the character is effected in the manner already described. The pulse S generated by the amplifier 146 (FIG. 4), passing through a delay circuit 186 (FIG. 5), where it is delayed for the time necessary for completing the printing of the character, reaches the AND gate 185, which is preset at the moment by the signal M4. From this gate it arrives through the OR gate 175 at the gate 166 preset by the signal issuing from the gate 170. The gate 166 now transmits a singlepulse to the first input of the counter 165, causing the motor 93 to rotate clockwise for one step and accumulating one unit in the counter 171.

If the carriage 64 is in the extreme right-hand position, one last character can be printed, but any further shifting of the carriage to the right is prevented. To this end, the two inputs of an AND gate 187 are energized by the signal 16 issuingfrom the counter 17! and by the signal issuing from the delay circuit 186. The output of the gate 187 is connected to a first input of a flip-flop 188 which, when it is switched by a pulse leaving the gate 187, causes the signal M of the gate 180 preventing the printing of any other charactenA second ll'lpilt of the flip-flop 188 can be activated by the signal l6, causing the flip-flop to return to the inoperative state as soon as the carriage 64 has left the end-of-line position.

When the carriage 64 is in the extreme right-hand position, the pulse issuing frornthe circuit 186 cannot reach'the cou nters 165 and 171 owing tothe absence of the signal 16 at the gate 166 and the carriage 64 will remain in the stationary position.

On depression of the usual space bar, the signal M4 is also generated as in the case of the printing keys, presetting the gates 166 and 167. At the same time, the space bar generates a pulse M5 which is sent to the gate 175, replacing the signal coming from the gate 185, as a result of which the carriage executes a step to the right as in the preceding case. I

Similarly, by depressing the usual back spacer, in addition tov the signal M4 which presets the gates 166 and 167 through the gate 170 a pulse M6 is sent to the gate 181. The pulse issuing from the gate 181 finds the gate 167 preset and arrives at the counter 165, as a result of which a step of the carriage 64 to the left is commanded. In order to obtain the return of the carriage to the beginning, the relevant operative key is depressed and generates a pulse M7 at the input of the gate 183. The flip-flop 184 is thus switched, presetting the gate 167 by means of the OR gates 182, 177 and 181 and presetting the gate 169 by means of the gate 176. The pulses supplied by the generator 168 therefore cause the carriage 64 to shift to the left as far as the extreme zero position. In correspondence with this position, the

beam emerging from the illuminating device 96 is received by the photoelectric cell 97, which brings the flip-flop 184 back to the initial state and thus interrupts the shifting of the carriage 64.

It is understood that various modifications and improvements may be made in the printer described without departing from the scope of the invention.

What I claim is:

l. A serial printing device for teleprinters and data processing systems in general, having a paper carrier, a type carrier, a carriage mounting one of said carriers, a reversible stepping motor, and means permanently connecting said motor with said carriage to transversely move said carriage in one of the two opposite directions along a printing line, and comprising an electronic register having a portion settable according to the transverse position required of said carriage, y i r an electronic counter, for constantlyindicating the current position of said carriage, said counter having a capacity corresponding to the number of positions that can be occupied by said carriage along the printing line,

a comparison circuit to compare the contents of said portion of said register with thecontents of said counter, v

a pulse generator for generating pulses at a predetermined frequency, v

direction control means controlled by said comparison circuit for selecting the direction of movement of said carriage,

first circuit means connecting said pulse generator with said stepping motor and controlled by said comparison circuitfor causing said motor to be driven in the selected direction a number of steps corresponding to'the pulses generated until said comparison circuit determines equality between the contents of said portion of said register and the contents of said counter, and 7 second circuit means connecting said pulse generator with said counter and controlled by said comparison circuit for causing said counter to count said pulses according to the selected direction,

whereby said counter constantly indicates the current position of said carriage. v 2. The device of claim 1, wherein said motor is provided with a number of windings activatable in sequences, and said direction control means comprise a sequential counter having a capacity equal to said number, and having two inputs to count said pulses, the pulses entering a first of said inputs generating signals at a number of outputs which in predetermined combinations activate said windings in a sequence producing a rotation of said motor in one direction, while the pulses entering the second of said inputsgenerate at said outputs signals which in other combinations activate said windings in another sequence producing a rotation of said motor in the opposite direction, said control means causing said pulses to enter one or the other of said inputs according to whether the contents of said register is lower or higher than that of said counter.

3. The device of claim 1, comprising means for effecting synchronization between the position of the carriage and said counter comprising a sensor for sensing the passage of said carriage through a predetermined position, zeroizing means controlled by said sensor when sensing said predetermined position to zeroize said counter, and manually actuatable means for disabling said comparison circuit and for causing said pulse generator to move said carriage toward said predetermined position, said manually actuatable means being disabled when said sensor senses said predetermined position.

4. A serial printing device for teleprinters and data processing systems in general, having a stationary frame, a paper platen rotatable on said frame, a type disc formed with a plurality of tongues each one provided with a type protruding from the flat surface thereof, said tongues being of flexible material, said disc being selectively rotatable on a substantially horizontal shaft perpendicular to said platen to locate a predetermined type in front of the printing point, a transversely movable carriage mounting said shaft, a

13, .a hammer mounted on said carriage and operableto strike against the tongue of the type so'located, and a pair of ribbon spools rotatably mounted on a pair of vertical shafts, wherein the improvement comprises:

means for removably mounting said disc on said horizontal shaft, an auxiliary frame pivotally mounted on said stationary frame coaxially with the shaft of one of said spools to facilitate the insertion of said paper on said platen or the removal of said dish-said transversely movable carriage being mounted on said auxiliary frame, at least a guide bar being fixed on said auxiliary frame for transversely guiding said carriage,

a pair of stepping motors mounted on said auxiliary frame for selectively moving respectively saidcarriage and said disk, and

locking means for locking said auxiliary frame on said stationary frame in a printing position. I

5. The device of claim 4, wherein said motor is provided with a number of windings activatable in sequences, and wherein said directioncontrol means comprise a sequential counter having a capacity equal to said number, and having two inputs to count said pulses and a number of outputs connected to said windings, the pulses entering a first of said inputs generating signals on said outputs in a predetermined sequence producing a rotation of said motor in one direction, while the pulses entering the second of said inputs generate signals on said outputs in another sequence producing a rotation of said motor in the opposite direction, said control means causing said pulses to enter one or the other of said inputs according to the selected direction of shortest route.

6. A serial printing device for teleprinters and data processing systems in general, having a type carrier carrying a plurality of types, means for rotatably mounting said type carrier to bring said types individually to a printing point upon being selectively rotated, a reversible stepping motor, and means permanently connecting said motor with said type carrier to rotate said type carrier in one of two opposite directions, and comprising:

a register having a portion settable according to the angular position required of said carrier,

a first counter for indicating the current angular position of said carrier, said counter having a capacity equal to the number of angular positions of said carrier,

a comparison circuit adapted to compare the contents of said portion of said register with the con tents of said counter,

a first pulse generator for generating pulses at a predetermined frequency,

another pulse generator for generating other pulses at a frequency substantially higher than the frequency of the first pulse generator,

another counter having a capacity equal to the number of angular positionsof said type carrier, said other counter being adapted to generate a first signal when it is loaded with less than half the pulses for which it has the capacity and a second signal when it is in the full state,

means controlled by said comparison circuit when no coincidence is determined for causing a number of pulses from said other generator equal to said capacity to simultaneously enter said. counters without driving said motor,

a bistable element for so controlling said direction control means as to bring the type to be printed to said printing point through the shortest route,

means controlled by said first signal in coincidence with a coincidence signal of said comparison circuit generated when it detennines that said contents are equal to drive said bistable element, and

control means controlled by said comparison circuit for causing said counter to count said pulses according to the selected direction and for causing said motor to be driven in the selected direction by said pulses till said comparison circuit determines equality between the contents of said portion of saidregister and the contents of said counter.

7. The device of claim 6, comprising:

driving means controlled by said second signal in absence of said coincidence signal for rendering said other pulse generator ineffective, and for causing said first named pulse generator to drive said .motor,

delay means for delay said coincidence signal to activa'te said first named pulse generator before said other pulse generator, said driving means rendering ineffective said first named pulse generator when said coincidence signal is generated.

I 8. The device of claim 6, whereinsaid type carrier is formed of a rotatable disc having a plurality of tongues each one provided with a type protruding from the flat surface thereof, said tongues being of flexible material, and comprising: 7

a hammer actuatable when the type to be printed is so located at the printing point to strike against the corresponding tongue, and

means controlled by said coincidence signal for actuating said hammer.

9. The device of claim 4, also comprising: a sensor for sensing the passagevof a type of said type carrier through a predetermined position, zeroizing means controlled by said sensor when sensing said passage of the type to send a reset signal to said counter for effecting synchronization between the angular position of said type carrier and said counter, and manually actuatable means for disabling said field indicating means and for causing said pulse generator to rotate said type carrier toward said predetermined position, said manually actuatable means being disabled when said sensor senses said passage of the type.

10. A serial printing device for teleprinters and data processing systems in general, having a paper carrier, a type carrier carrying a plurality of types, a carriage rotatably mounting said type carrier and transversely movable with respect to said paper carrier, a pair of reversible stepping motors, means permanently connecting a first one of said motors with said carriage to transversely move said carriage in one of two opposite directions in letter spaced positions, a second of said motors being mounted on said carriage, and means permanently connecting said second motor with said type carrier to rotate said carrier in one of two opposite directions, and comprising:

a register having a first portion adapted to store a first code combination representing the transverse position in which a type is to be printed, and a second portion adapted to store a second code combination representing the type to be printed,

ing the current position of said carriage and having a capacity corresponding to the number of said letter spaced positions in a printing line, the other counter indicating the current angular position of said type carrier and having a capacity corresponding to the number of said types,

a pair of comparison circuits to compare said code combination with the contents of said counters,

a pair ofpulse generators associated with said motors for generating pulses at predetermined frequencies corresponding to the requisite speed of said carriage and of said type carrier, 7

field indicating means operable when said carrier is standing to indicate the field presently at the printing point, I

a pair of direction control means associated with said motors, a first one of said direction control means being controlled by one ofsaid comparison circuits for selecting the direction of movement of said carriage, the other direction control means being jointly controlled by the other of said comparison circuits and by said field indicating means for selecting the direction of rotation of said type carrier, a I

.a pair of first control circuits connecting saidpulse generators with the corresponding motors and controlled by said comparison circuits for causing the associated motors to be driven to move said carriage and to rotate said type carrier' in the selected direction by the pulses generated until each of said comparison circuits determines equality between the contents in the associated 5 16 parison circuit associated with said first motor, and space means conditionable at the depression of any alphanumeric key for generating a space signal for end portion of the register and the contents in the associated counter, and

a pair of second control circuits controlled by said comparison circuits connecting said pulse generators with the associated counters and controlled by said comparison circuits for causing said counters to count said pulses according to the selected directions of movement and of rotation.

11. T he device of claim 10 including alphanumeric key responsive means for loading the second portion of said register with a code combination representing the character to be printed and for loading the first portion of said register with a predetermined constant combination, means responsive to said predetermined constant combination for rendering inactive the comcausing the direction control means associated with said first motor to advance said carriage one letter space.

12. The device of claim 11, also comprising: a hammer actuatable-for printing the selected type, a hammer actuating circuit controlled by the comparison circuit associated with said second motor, said actuating circuit generating a delay signal simultaneously with said hammer actuation, and a delay circuit controlled by said delay signal for causing said space means to generate said space signal after said hammer actuation.

13. The device of claim ,12, wherein the counter as- I sociated with said first motor is adapted to generate an line signal, and comprising means controlled by said end line signal for preventing said delay circuit from so causing said space means to generate said signall. Y

14. A serial printing device for teleprinters and data processing systems in general, "having a stationary frame, a paper platen rotatable on said frame, a type disc formed with a plurality of tongues each one provided with a type protrudingfrom the flat surface thereof, said-tongues being of flexible material, said disc being selectively rotatable on a substantially horizontal shaft perpendicular to said platen to locate a predetermined type in front of the printing point, a transversely movable carriage mounting said shaft, a hammer mounted on said carriage and operable to strike against the tongue of the type so located, and a pair of ribbon spools rotatably mounted on a pair of vertical shafts, wherein the improvement comprises:

means for removably mounting said disc on said horizontal shaft, an auxiliary frame .pivotally mounted on said stationary frame coaxiallywith the shaft of one of said spools to facilitate the insertion of said paper on said platen or the removal of said disk,

at least a guide bar fixed on said auxiliary frame for UNITED STATES PATENT OFFlCE c-ERT FIcATE OF coRRtcT'ioN Patent No. 3, 707, 214 Dated December 26, 1972 -Inventor(s) Gian L. Ponzano It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cancel claim 14.

Insert the following claim:

A serial printing device for tel'eprinters and data processing systems in general, having a type carrier carrying a plurality of types, means for rotatably mounting said type carrier to bring said types individually to a printing point upon being selectively rotated, said type carrier being divided into two similar fields covering 180 degrees of said carrier, a reversible stepping motor, and means permanently connecting said motor with said type carrier to rotate said type carrier in one of two opposite directions, and comprising:

an electronic register having a portion settable according to the angular position required of said carrier,

' an electronic counter for indicating the current angular position of said carrier, said counter having a capacity corresponding to the number of angular positions of said carrier,

a comparison circuit adapted to compare the contents of said portion of register with the contents of said counter,

, a pulse generator for generating pulses at a predetermined frequency,

field indicating means operable when said carrier is standing to indicate the field presently at the printing point,

FORM PO-1050 (10-69) USCOMM-DC GOING-P69 W U,5. GOVERNMENT PRINTING OFFICE: 19'9 0-366-334,

- UNITED STATES 'PATENTDFFICE CERTIFICATE OF CORRECTION Patent No. 3,707,214 Dated December 26; 1972 Inventor-(s) Gian L. Ponzano I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

, direction control means jointly controlled by said comparison I circuit and said field indicating means for so selecting the direction of rotation of said motor as to bring the type of said carrier to be printed to said printing point through the shortest route,

first circuit means connecting said pulse generator with said stepping motor and controlled by said direction control means for causing said motor to be driven in the selected direction a number of steps corresponding to the number of pulses generated until said comparison circuit determines equality between the contents of said portion of register and the contents of said counter, and

second circuit means connecting said pulse generator with J said counter and controlled by said direction control means for causing said counter to count said pulses according to the selected direction.

Signed and sealed this 8th day of October 1974.

- (SEAL) Attest: I

McCOY M. GIBSON JR. C. MARSHALLDANN Attesting Officer Commissioner" of Patents FORM PO-1050 (10-69) v uscoMM-oc suave-pee fi UlS. GOVERNMENT PRlNTlNG OFFICE I969 0-366-3 

1. A serial printing device for teleprinters and data processing systems in general, having a paper carrier, a type carrier, a carriage mounting one of said carriers, a reversible stepping motor, and means permanently connecting said motor with said carriage to transversely move said carriage in one of the two opposite directions along a printing line, and comprising : an electronic register having a portion settable according to the transverse position required of said carriage, an electronic counter for constantly indicating the current position of said carriage, said counter having a capacity corresponding to the number of positions that can be occupied by said carriage along the printing line, a comparison circuit to compare the contents of said portion of said register with the contents of said counter, a pulse generator for generating pulses at a predetermined frequency, direction control means controlled by said comparison circuit for selecting the direction of movement of said carriage, first circuit means connecting said pulse generator with said stepping motor and controlled by said comparison circuit for causing said motor to be driven in the selected direction a number of steps corresponding to the pulses generated until said comparison circuit determines equality between the contents of said portion of said register and the contents of said counter, and second circuit means connecting said pulse generator with said counter and controlled by said comparison circuit for causing said counter to count said pulses according to the selected direction, whereby said counter constantly indicates the current position of said carriage.
 2. The device of claim 1, wherein said motor is provided with a number of windings activatable in sequences, and said direction control means comprise a sequential counter having a capacity equal to said number, and Having two inputs to count said pulses, the pulses entering a first of said inputs generating signals at a number of outputs which in predetermined combinations activate said windings in a sequence producing a rotation of said motor in one direction, while the pulses entering the second of said inputs generate at said outputs signals which in other combinations activate said windings in another sequence producing a rotation of said motor in the opposite direction, said control means causing said pulses to enter one or the other of said inputs according to whether the contents of said register is lower or higher than that of said counter.
 3. The device of claim 1, comprising means for effecting synchronization between the position of the carriage and said counter comprising a sensor for sensing the passage of said carriage through a predetermined position, zeroizing means controlled by said sensor when sensing said predetermined position to zeroize said counter, and manually actuatable means for disabling said comparison circuit and for causing said pulse generator to move said carriage toward said predetermined position, said manually actuatable means being disabled when said sensor senses said predetermined position.
 4. A serial printing device for teleprinters and data processing systems in general, having a stationary frame, a paper platen rotatable on said frame, a type disc formed with a plurality of tongues each one provided with a type protruding from the flat surface thereof, said tongues being of flexible material, said disc being selectively rotatable on a substantially horizontal shaft perpendicular to said platen to locate a predetermined type in front of the printing point, a transversely movable carriage mounting said shaft, a hammer mounted on said carriage and operable to strike against the tongue of the type so located, and a pair of ribbon spools rotatably mounted on a pair of vertical shafts, wherein the improvement comprises: means for removably mounting said disc on said horizontal shaft, an auxiliary frame pivotally mounted on said stationary frame coaxially with the shaft of one of said spools to facilitate the insertion of said paper on said platen or the removal of said disk, said transversely movable carriage being mounted on said auxiliary frame, at least a guide bar being fixed on said auxiliary frame for transversely guiding said carriage, a pair of stepping motors mounted on said auxiliary frame for selectively moving respectively said carriage and said disk, and locking means for locking said auxiliary frame on said stationary frame in a printing position.
 5. The device of claim 4, wherein said motor is provided with a number of windings activatable in sequences, and wherein said direction control means comprise a sequential counter having a capacity equal to said number, and having two inputs to count said pulses and a number of outputs connected to said windings, the pulses entering a first of said inputs generating signals on said outputs in a predetermined sequence producing a rotation of said motor in one direction, while the pulses entering the second of said inputs generate signals on said outputs in another sequence producing a rotation of said motor in the opposite direction, said control means causing said pulses to enter one or the other of said inputs according to the selected direction of shortest route.
 6. A serial printing device for teleprinters and data processing systems in general, having a type carrier carrying a plurality of types, means for rotatably mounting said type carrier to bring said types individually to a printing point upon being selectively rotated, a reversible stepping motor, and means permanently connecting said motor with said type carrier to rotate said type carrier in one of two opposite directions, and comprising: a register having a portion settable according to the angular position required of said carrier, a first counter for indicating the current angular position of saiD carrier, said counter having a capacity equal to the number of angular positions of said carrier, a comparison circuit adapted to compare the contents of said portion of said register with the contents of said counter, a first pulse generator for generating pulses at a predetermined frequency, another pulse generator for generating other pulses at a frequency substantially higher than the frequency of the first pulse generator, another counter having a capacity equal to the number of angular positions of said type carrier, said other counter being adapted to generate a first signal when it is loaded with less than half the pulses for which it has the capacity and a second signal when it is in the full state, means controlled by said comparison circuit when no coincidence is determined for causing a number of pulses from said other generator equal to said capacity to simultaneously enter said counters without driving said motor, a bistable element for so controlling said direction control means as to bring the type to be printed to said printing point through the shortest route, means controlled by said first signal in coincidence with a coincidence signal of said comparison circuit generated when it determines that said contents are equal to drive said bistable element, and control means controlled by said comparison circuit for causing said counter to count said pulses according to the selected direction and for causing said motor to be driven in the selected direction by said pulses till said comparison circuit determines equality between the contents of said portion of said register and the contents of said counter.
 7. The device of claim 6, comprising: driving means controlled by said second signal in absence of said coincidence signal for rendering said other pulse generator ineffective, and for causing said first named pulse generator to drive said motor, delay means for delay said coincidence signal to activate said first named pulse generator before said other pulse generator, said driving means rendering ineffective said first named pulse generator when said coincidence signal is generated.
 8. The device of claim 6, wherein said type carrier is formed of a rotatable disc having a plurality of tongues each one provided with a type protruding from the flat surface thereof, said tongues being of flexible material, and comprising: a hammer actuatable when the type to be printed is so located at the printing point to strike against the corresponding tongue, and means controlled by said coincidence signal for actuating said hammer.
 9. The device of claim 4, also comprising: a sensor for sensing the passage of a type of said type carrier through a predetermined position, zeroizing means controlled by said sensor when sensing said passage of the type to send a reset signal to said counter for effecting synchronization between the angular position of said type carrier and said counter, and manually actuatable means for disabling said field indicating means and for causing said pulse generator to rotate said type carrier toward said predetermined position, said manually actuatable means being disabled when said sensor senses said passage of the type.
 10. A serial printing device for teleprinters and data processing systems in general, having a paper carrier, a type carrier carrying a plurality of types, a carriage rotatably mounting said type carrier and transversely movable with respect to said paper carrier, a pair of reversible stepping motors, means permanently connecting a first one of said motors with said carriage to transversely move said carriage in one of two opposite directions in letter spaced positions, a second of said motors being mounted on said carriage, and means permanently connecting said second motor with said type carrier to rotate said carrier in one of two opposite directions, and comprising: a register having a first portion adapted to store a first code combination represenTing the transverse position in which a type is to be printed, and a second portion adapted to store a second code combination representing the type to be printed, a pair of counters, a first one of said counters indicating the current position of said carriage and having a capacity corresponding to the number of said letter spaced positions in a printing line, the other counter indicating the current angular position of said type carrier and having a capacity corresponding to the number of said types, a pair of comparison circuits to compare said code combination with the contents of said counters, a pair of pulse generators associated with said motors for generating pulses at predetermined frequencies corresponding to the requisite speed of said carriage and of said type carrier, field indicating means operable when said carrier is standing to indicate the field presently at the printing point, a pair of direction control means associated with said motors, a first one of said direction control means being controlled by one of said comparison circuits for selecting the direction of movement of said carriage, the other direction control means being jointly controlled by the other of said comparison circuits and by said field indicating means for selecting the direction of rotation of said type carrier, a pair of first control circuits connecting said pulse generators with the corresponding motors and controlled by said comparison circuits for causing the associated motors to be driven to move said carriage and to rotate said type carrier in the selected direction by the pulses generated until each of said comparison circuits determines equality between the contents in the associated portion of the register and the contents in the associated counter, and a pair of second control circuits controlled by said comparison circuits connecting said pulse generators with the associated counters and controlled by said comparison circuits for causing said counters to count said pulses according to the selected directions of movement and of rotation.
 11. The device of claim 10 including alphanumeric key responsive means for loading the second portion of said register with a code combination representing the character to be printed and for loading the first portion of said register with a predetermined constant combination, means responsive to said predetermined constant combination for rendering inactive the comparison circuit associated with said first motor, and space means conditionable at the depression of any alphanumeric key for generating a space signal for causing the direction control means associated with said first motor to advance said carriage one letter space.
 12. The device of claim 11, also comprising: a hammer actuatable for printing the selected type, a hammer actuating circuit controlled by the comparison circuit associated with said second motor, said actuating circuit generating a delay signal simultaneously with said hammer actuation, and a delay circuit controlled by said delay signal for causing said space means to generate said space signal after said hammer actuation.
 13. The device of claim 12, wherein the counter associated with said first motor is adapted to generate an end line signal, and comprising means controlled by said end line signal for preventing said delay circuit from so causing said space means to generate said signal.
 14. A serial printing device for teleprinters and data processing systems in general, having a stationary frame, a paper platen rotatable on said frame, a type disc formed with a plurality of tongues each one provided with a type protruding from the flat surface thereof, said tongues being of flexible material, said disc being selectively rotatable on a substantially horizontal shaft perpendicular to said platen to locate a predetermined type in front of the printing point, a transversely movable carriage mounting said shaft, a hammer mounted on said carriage and oPerable to strike against the tongue of the type so located, and a pair of ribbon spools rotatably mounted on a pair of vertical shafts, wherein the improvement comprises: means for removably mounting said disc on said horizontal shaft, an auxiliary frame pivotally mounted on said stationary frame coaxially with the shaft of one of said spools to facilitate the insertion of said paper on said platen or the removal of said disk, at least a guide bar fixed on said auxiliary frame for transversely guiding said carriage, a pair of stepping motors mounted on said auxiliary frame for selectively moving respectively said carriage and said disk, and locking means for locking said auxiliary frame on said stationary frame in a printing position. 